The effects of sex and age on phytohaemagglutinin skin-testing of deer.

Aim: To determine if there are sex- or age-related differences in the increase in skinfold thickness in response to the mitogen phytohaemagglutinin (PHA) in red deer.

Methods: One dose of 250 mug PHA was injected intradermally in the right side of the neck, and phosphate buffered saline (PBS) was injected at a second site as a control, in 110 (51 males and 59 females) captive Iberian red deer (Cervus elaphus hispanicus), ranging in age from 21 months to > or =5 years. Skinfold thicknesses were measured immediately before and 72 h following injection.

Results: There was a significant effect of gender on the average increase in skinfold thickness; males had greater increases (8.8 (SEM 0.57) mm) than females (4.23 (SEM 0.39) mm) after correcting for other confounding variables. No age-related differences were evident, but differences between sexes were more marked with increasing age.

Conclusions And Clinical Relevance: Effects of gender, probably due to differences in energetic and reproductive constraints in red deer, should be taken into account when interpreting skinfold-test data, both in ecology and in the control of tuberculosis (Tb). Males tend to have a thicker skin than females, so skinfold increase relative to the thickness of the skin, rather than skinfold increase per se, should be used as a more appropriate measure of skinfold increase. This may also have clinical relevance in the interpretation of tuberculin skin testing.